The notice said attendance for the quarter that ended March 31 dropped to about 3.05 million visitors from 3.5 million in the same period in 2013.

A SeaWorld spokesman declined to comment but pointed to previous financial reports that showed the company expects attendance numbers to change with the shift of holidays in the calendar. Easter, for example, took place in the first quarter of 2013, but in 2014 the holiday falls in the second quarter.

The Orlando theme park company has been under scrutiny by animal rights activists since the release last year of a documentary film, "Blackfish," that suggests the parks mistreat their killer whales.

But during a conference call last month to report 2013 financial results, SeaWorld officials rejected suggestions that the company is suffering because of a backlash from the film.

For the year, attendance at the company's 11 parks dropped 4.1% to 24.4 million, but the decline was offset by higher admission prices and greater in-park spending. SeaWorld officials instead attributed the attendance drop to a rise in theme park ticket prices last year.

New York-based Blackstone bought SeaWorld Entertainment from Anheuser-Busch InBev for $2.3 billion in 2009. Blackstone launched an initial public offering of the company last year.

The repurchase of SeaWorld shares coincides with the sale by Blackstone of 15 million shares.

Blackstone's sale of SeaWorld shares this week had "absolutely nothing to do" with the Blackfish controversy, said Peter Rose, senior managing director for Blackstone.

He said Blackstone's long-term plan has been to take SeaWorld public, divest itself from the theme park company and "return money to our investors."